Girls’ education is emerging as one of the top priorities of the international development community. United Nations Secretary-General Kofi Annan has said that “educating girls is not an option, it is a necessity,” and the 189 countries that signed up for the Education for All (EFA) initiative in 2000 showed their support by pledging to eliminate gender disparities in education by 2005.

Much progress has been made in recent decades. The number of girls attending school, even in the poorest countries, has grown rapidly in the past 50 years. High-income countries have achieved full equality of access to education, and in the developing regions of Latin America, East Asia, and the Middle East, almost as many girls as boys now attend school.

In some developing regions, however, millions of girls still receive little or no education. South Asia and sub-Saharan Africa are far from meeting the EFA target, and progress in Central Asia has slowed in the last decade. Of the more than one hundred million children in the world without access to primary schooling, 60 percent are girls, and in countries like Afghanistan, Niger, Nepal, and Yemen, female literacy is less than half that of males.

These disparities hurt not just girls themselves, but also their families and the societies in which they live. Girls suffer because they miss out on opportunities to socialize, acquire knowledge, and gain the skills and sense of autonomy needed to improve their personal well-being and their lot in life. Each additional year of schooling tends to increase an individual’s earnings by more than 15 percent, and education also improves women’s health and gives them a greater say in how their lives are conducted.

Families suffer, too, if girls are not educated. Mothers with education use the knowledge they have acquired to improve the health of their children and other family members. In South Asia and sub-Saharan Africa children whose mothers have received secondary schooling are twice as likely to be immunized against major disease as those whose mothers had not been to school. Educated mothers provide better nutrition to their children, too, and their knowledge of health risks protects their families against illness and promotes health-seeking behavior more generally. As a consequence, child mortality rates are much higher in families where the mother lacks education than in families where both parents have attended school. In sub-Saharan Africa, for example, children whose mothers have more than seven years of schooling have less than half the under-5 mortality rate of the children of uneducated mothers.

The benefits to societies are also great. Girls’ education is now recognized as a cornerstone of development. Educated mothers invest more in their children’s schooling, thus improving both families’ and societies’ development prospects. They are also likely to have fewer children. For example, in Brazil, women with a secondary education have an average of 2.5 children, whereas illiterate women have an average of 6.5 children. Having fewer children allows families to invest more in the health and education of each child, thereby raising the productivity of future generations.

Of course, leaving women uneducated dramatically reduces the productive capacity of present generations too. Economies that fail to make use of the skills of half their potential workforce are at a huge disadvantage relative to those where everyone is contributing to the best of their ability. World Bank economists David Dollar and Roberta Gatti have studied the effect of girls’ education on economies. The return on investment in girls’ education, they find, is not lower than the return for boys and, particularly in lower-middle-income countries, is often significantly higher. Dollar and Gatti conclude that economies “that have a preference for not investing in girls pay a price for it in terms of slower growth and reduced income.”

Why, then, have some countries failed to close the gap? The main causes are cultural and economic. Schools in some developing countries are insensitive to girls’ needs. Verbal and physical abuse, a lack of sanitation, and long distances between home and school can all make schooling a hazardous experience and deter parents from sending their daughters to school. Certain cultural practices also make sending girls to school less desirable. In many societies, girls are not expected to make economic contributions to their families. Instead, they are expected to care for family members and carry out household chores, tasks for which education is not seen as necessary. Moreover, girls are seen as relatively transitory assets — not worthy of long-term investment — as they leave their parents’ household upon marriage. A vicious cycle is thereby created: Girls are believed to be less worthy of education so they receive less, which diminishes women’s prospects of closing the gap on men in the future.

Even where families are willing to invest in their daughters’ schooling, discrimination in the labor market can make investing in boys before girls a rational economic decision. In developing countries, women earn less than men even if they have the same education and experience, so the economic returns to individuals mean that boys’ schooling is inevitably seen as a better investment. The disparity is magnified by the fact that women tend to have less access to financial capital and less secure claims to financial capital and other assets than men. This perspective does not, of course, take into account the social benefits of girls’ education, but economic gains are a powerful driver of family decisions, particularly in poorer societies.

Promoting girls’ education, therefore, involves changing attitudes across society as well as spending money on increasing the number of school places available to girls. Donors providing funding for education can help by insisting that their funds are used to educate girls as well as boys. New means of engaging policy makers — perhaps through a bottom-up approach, where pressure is applied by civil society, or through better use of evidence to show the benefits of girls’ schooling — may also reap rewards. Religious leaders also need convincing, as do men in general, who are usually the main decision makers within households. Changing cultural attitudes toward women is a slow and difficult process. In those nations that have succeeded, such changes have typically required strong political leadership.

Businesses, too, need to change their ways by providing opportunities to women, since they are likely to benefit from access to both a deeper pool of well-trained labor and the skills and knowledge women bring to a task. The World Bank has found that gender-biased hiring and pay practices are more common in firms that have little or no competition, but as economies open up, employment prospects for women should improve and justify investment in their education.

Even if governments and businesses are persuaded, however, reforming education systems to increase girls’ attendance is no easy task. Those countries with the greatest disparities in access to education, like Afghanistan, India, Ethiopia, and Yemen, are among the poorest countries in the world. Building new schools, improving sanitation in existing schools, reducing costs so that schooling is more affordable for families, and convincing families of the value of girls’ schooling require significant resources. For resource-strapped governments, many of these tasks are out of reach.

In such circumstances, a focus on the bare necessities is likely to pay dividends, and the critical factor in determining whether attending school is a rewarding experience is the quality of teaching. A good education can be delivered without buildings, uniforms, or even books, but it cannot be achieved without good teachers. Training and attracting women teachers should be a high priority for poor countries attempting to educate girls. Women teachers make families more comfortable about sending their daughters to school, and they are more sensitive to girls’ needs. Many developing countries already have high ratios of women to male teachers, but the historic neglect of girls’ education means that many of these women are poorly trained themselves.

Those countries that have lagged in promoting girls’ education have also lagged developmentally. It is expensive — both politically and financially — to eliminate gender gaps in school enrolment. But if developing countries wish to improve their living standards and catch up with the industrialized world, not educating one’s girls to the same extent as boys will surely prove even more expensive.

David Bloom is Clarence James Gamble Professor of Economics and Demography at Harvard University. He is also a co-principal investigator of an American Academy of Arts and Sciences project on universal basic and secondary education (UBASE). This project has assembled a task force to examine the rationale, means, and consequences of providing a quality education to all the world’s children at the primary and secondary levels. Mark Weston researches and writes on issues of international development, mainly in the areas of governance, health, and education, for a variety of organizations.